So I've run through the tuorials and read what the manual has to say about groups and I have learned two thinbgs only about them:

1. If you make a stack a group then you no longer see the constituent units in the stack panel, just the leader.2. If you make a stack a group then they will only require a maximum of 4 command points, meaning that a lesser general can command a larger force without penalty.

From this information there appears to be no reason at all not to make all stacks commanded by lesser leaders groups since it just eliminates any problems relating to command point requirments - any leader can lead any group of up to eight units with no command penalty.

But that tells me I must be missing something since if that was so then why not just apply a maximum command point requirement of four to every stack in the first place and not bother with this group thing?

Ah, I've just remembered somwehre it said that if a stack was a group then it benefited from bonuses derived from both thhe group leader and the stack leader. But I can't see how you designate two leaders to a group and specify one as the group leader and the orther is the stack leader (nor does that make any sense to me really).

So since neither the tutorial or the manual tell me the answer to this, and I can't find any stickies hhere or on the AGEOD froum that explainsd this in more detail can somebody explain what I am missing here?

Why are groups in the game at all, under what circumstances would you not want turn a stack into a group, and what are you supposed to do with groups, what's the main reason for them?

I think I am more confused by your question than by the game situation you are trying to solve, but I will attempt to shed some light on the issue.

Military forces in TYW are (from smallest to largest) 'units' (individual regiments and squadrons), 'groups' (several regiments/squadrons under a single commander) and 'wings' (several groups operating under a single general).

'Groups' are therefore sub-formations within a 'wing'. The purpose of groups is to reduce the number of command points necessary to lead the wing in combat. A large wing will have 3-4 groups along with supply, artillery and perhaps cavalry units attached but not assigned to a group. Wings without enough command points will suffer a combat penalty (shown as a negative % in the wing's tab). Since military forces are expensive to raise and replace, fighting with a command point penalty should be avoided as much as possible! Small forces - garrisons and security units - may have to fight without a commander, however, since each side has a limited pool of leaders.

Generally speaking, each side in the conflict will have their forces organized into 1-3 wings each led by a 3-star or senior 2-star general. Effective combat power of each wing will be 1000-2000 points, depending on strategic and supply considerations. Larger forces require more supplies and may be subject to movement penalties.

Ripster8's answer is pretty complete. Two other things to think about:1. The leader in command provides his qualities to all units beneath. The sub-commanders who have organized wings provide, in addition, their qualities to the units they command.2. The primary time you might not want to have units in stacks is when they are raiding units, like a Hungarian patrol.